Total length = number of intervals × interval length

Interval length = total length ÷ number of intervals

Number of intervals = total length ÷ interval length

Tree planting problem

(1) Planting trees at both ends;

Tree = interval+1

(2) planting only one end:

Tree = number of intervals

(3) No planting at both ends: tree = interval-1

(4) Closed: tree = interval number.

Example:

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